Preparation of sheet metal for enameling



Dec. 18, 1956 c. J. RODMAN 2,774,678

PREPARATION OF SHEET METAL FOR ENAMELING Filed April 21, 1953 2 Sheets-Sheet 1 FIG. I

INVEN TOR.

CLARENCE J. RODMAN ATTORNEY Dec. 18, 1956 c. J. RODMAN PREPARATION OF SHEET METAL FOR ENAMELING 2 Sheets-Shee t 2 Filed April 21, 1953 INVENTOR FIG. 4

I Po /my ATTORNEY PREPARATION OF SHEET METAL FOR ENAMELING Clarence J. Rodman, Alliance, Ohio, assignor, by mesne assignments, to AllianceWare, Inc., a corporation of Delaware Application April 21, 1953, Serial No. 350,017

5 Claims. (Cl. 117-8) This invention relates to the preparation of iron sheet products for porcelain-enameling. The treatment is applicable to the de-enameling of enameled ware and to the preparation of sheet iron which has not been enameled. The treatment involves the bombardment of the surface of the metal with very fine shot, and if the treatment is applied to enameled ware the bombardment first removes the enamel coat.

In all commercial enameling porcelain-enameling a certain percentage of the enameled products are defecto an objectionable temperature. Shot which is substantially the size of S-170 shot when projected at a speed of 2.5 to 3.0 miles per minute works the surface of the unenameled sheet, and removes all traces of enamel from the enameled sheet and then works its surface, all without heating the surface unduly. i

Bombardment of products formed from high grade iron sheet has been found highly desirable,particularly if the iron is covered with a thin coating of copper or nickel or other metal electropositive, to iron,,. as is common practice to prevent the ironfrom rusting This coating may be applied after or during the pickling, likewise it may be applied to metal which has not been subjected to pickling. The shot bombardment removes all scale and dirt from the metal surface and thus eliminatesthe necessity of pickling before enameling, although as indicated, the sheet may be pickled if desired. The working of the metal surface prepares it in some way so that on the subsequent application of fresh enamel to it, a stronger bond is formed than if the metal surface has not. been first bombarded by the shot. 7 V

Drawnmetal shapes, the surfaces of which have been worked according to this invention, may beenameled without first performing any additional operation for removing the draw coat. .Draw coats of inorganic matter are readily removed by the bombardment, together with scale and other dirt. If the bombardment of this invention is used to clean a sheet on which there remains a draw coat of oil or grease or soap or other material soluble in organic solvent, the shot will become coated with: the draw coat and will eventually stick together and less valuable because of the inferior coating. By removing the inferior coating and replacing it with a perfect coating the product can be disposed of as first-class merchandise. The shot first crack the enamel and then chip it from the base metal. After removing it they work the surface of the metal.

The process has a very beneficial effect on the surface of sheet iron whether or not it has ever been enameled. The surface of the metal is not abraded, as is the case when the metal is bombarded with grit, but the shot rolls the surface, covering it with small pock marks, making it more receptive for the enamel so that when the enamel is applied it adheres tenaciously. Any usual process of enameling may be used on the worked surface.

The shot employed is an antimony shot or other metallic shot which is high in the scale of hardness as compared with the base metal. This prevents the metal of the shot from being deposited on the sheet metal. 7

Shot known as S-170 True Steel shot has been found satisfactory. This shot is relatively fine. The specifications require that all of it pass through a 20 screen (.0331 inch aperture), no more than 10 percent is to be retained on a 25 .screen (.028 inch aperture), a minimum of 75 percent is to pass through a 25 screen and be retained on a 40 screen (.0165 inch aperture), a maximum of 12 percent is to pass through a 40 screen and be retained on a screen (.0138 inch aperture), and a maximum of 3 percent is to be retained on a 45 screen. More generally it may be said that the shot are relatively uniform in size ably one which projects all of the shot at substantially the same speed. The spraying equipment shown includes a 4 and the greater part of thempass through a screen with a .03 inch aperture and are retained on a screen with a .015 inch aperture.

The shot is projected against the surface whether enameled or not, at high speed. Speeds which are constant in the range of 2.5 to 3.0 miles per minute have been found satisfactory. Higher speeds or the same speeds with larger shot will heat the bombarded surface to the sheet unless cleaned by the solvent which may, for example, be carbon tetrachloride. A preferable manner of cleaning the shot will be to pass it through vapor of the carbon tetrachloride or other solvent. Thus, each shot may be cleansed before reuse, or the cleaning treatment may be applied only after the shot has been reused several times. Preferably shot used in the process will be recovered and cleansed enroute to the device in which it is to be again projected against the same or a different surface.

The invention will be described in connection with the accompanying drawings, in which:

Fig. 1 is a plan view, partly broken away, of equipment spraying iron sheet; v I r Fig. 2 is an enlarged section through the spraying equipment on the line 2--2 of Fig. 1;

Fig. 3 is an enlarged section through the spraying equipment on the line 3-'-3 of Fig. 2; and

Fig. 4 is a photograph, enlarged to three times actual size, of iron sheet which has been rolled by bombardment with relatively fine shot as here described.

The drawings show the treatment of a fiat sheet 1 of vantageously adjusted to travel at a slower speed than for merely working an unenameled surface. S

Any suitable spraying means may be used. It is preferwheel withradial vanes 5 mounted on a hollow axis 6 with an opening 7 in one side through which the shot are fed from a supply pipe 8 on to the vanes. The vaned wheel is rotated at high speed by the motor 9 mounted on the support 10. The opening is on one side of the axis and this projects the shot in a relatively narrow arc. The spraying is carried out in a chamber 15, to prevent loss of the shot, and the products in leaving the chamber preferably push their way out through curtained opening 16, because the shot ricochets from one wall to the other, and to and from the product.

The chamber may be covered on the interior with the type of backing used behind the target on a rifle range. To prevent shot from coming out through the openings through which the'products are conveyed, these openings may be labyrinthiform, in which case the track will be curved to follow them.

The bottom of the enclosure may advantageously slant toward a collection point from which the shot will be drawn off through suitable means and reused.

The operation will ordinarily be carried out on a continuous basis as the product is moved along at a slow rate of speed through the hail of shot. The surface of the product will be worked, and enameled products will be tie-enameled as they are passed between the sprays of shot within the enclosure. De-enameled products may be removed from the conveyor and placed with like products which have never been enameled, but are freshly pickled or otherwise pre-treated for enameling.

The treatment may be applied to only one or to both surfaces of the product. If applied to both surfaces, both surfaces may be bombarded simultaneously, or one may be bombarded first and then the other.

This application is a continuation-in-part of my applications Serial Nos. 258,694 and 258,695 filed November 28, 1951, both now abandoned.

What I claim is:

1. The process which comprises working the surface of an iron sheet product by bombarding it with relatively fine metallic shot, the shot being high in the scale of hardness compared to the iron sheet, whereby the worked surface is covered with peck marks, and then porcelainenameling the surface.

2. The process which comprises working a porcelainenameled iron sheet product by bombarding it with relatively fine metallic shot, the shot being high in the scale of hardness compared to the iron sheet, and thereby deenameling and working the surface of the product, and then porcelain-enameling the surface.

3. The process of working the surface of an iron sheet product covered with a thin coating of a surface electropositive to the iron, which comprises working the surface by bombarding it with relatively fine metallic shot, the shot being high in the scale of hardness compared to the iron sheet, and then porcelain enameling the surface.

4. The process of conditioning drawn iron sheet prior to poreclain-enameling, the metal having thereon draw coat which is soluble in organic solvent, which process comprises Working the surface of the sheet and simultaneously removing the draw coat by bombarding the surface with relatively fine metallic shot, the shot being high in the scale of hardness compared to iron, whereby no metal of the shot is deposited on the surface being worked.

5. The process which includes the conditioning process of claim 4 followed by porcelain-enameling the bombarded surface.

References Cited in the file of this patent UNITED STATES PATENTS 2,158,063 Broadfield May 16, 1939 l,l7l,300 Castle Aug. 29, 1939 2,182,132 Matthes Dec, 5, 1939 2,249,678 Wallace July 15, 1941 2,434,881 Dill Jan. 20, 1948 2,442,485 Cook June 1, 1948 

1. THE PROCESS WHICH COMPRISES WORKING THE SURFACE OF AN IRON SHEET PRODUCT BY BOMBARDING IT WITH RELATIVELY FINE METALLIC SHOT, THE SHOT BEING HIGH IN THE SCALE OF HARDNESS COMPARED TO THE IRON SHEET, WHEREBY THE WORKED SURFACE IS COVERED WITH POCK MARKS, AND THEN PORCELAINENAMELING THE SURFACE. 